Every year the warnings go out alerting parents to be on the watch for marijuana-laden treats that look like candies or cookies. And every year (for decades) no such case has been found. It (and the razor blade in the apple meme) were debunked a long time ago.
But rather than ignore this silliness completely, make a note of where the warning you heard came from, it’s (human) source.
Otherwise, parents, throw out anything from your kid’s bag that looks suspicious, and keep the cannabis edibles you find in a child-proof place for later….